Imaging Device Charge-Blocking Layers for Reduced Parasitic Sensitivity
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Solution Overview
Problem
Existing imaging devices suffer from high parasitic sensitivity due to the migration of electrons and holes across electrodes, which affects the signal-to-noise ratio.
Innovation Solution
The imaging device incorporates a photoelectric conversion layer with donor and acceptor semiconductor materials, along with charge blocking layers and a charge storage region, where the ionization potentials and electron affinities are strategically aligned to prevent electron and hole migration, respectively, and employs a voltage supply circuit to separate photoconversion and reading timings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If charge blocking layers are added to prevent electron and hole migration, then parasitic sensitivity is reduced, but device structure becomes more complex
Solution Approach 1:
The patent introduces charge blocking layers as intermediary components between the electrodes and the photoelectric conversion layer. These blocking layers act as mediators that prevent direct charge migration while allowing the photoelectric conversion function to operate. The first charge blocking layer prevents electron migration, and the second charge blocking layer prevents hole migration, thereby reducing parasitic sensitivity without fundamentally changing the photoelectric conversion mechanism.
Solution Approach 2:
The patent employs composite material structures by combining the photoelectric conversion layer with charge blocking layers having specific energy level characteristics. The charge blocking layers are selected or designed with ionization potentials and electron affinities that create energy barriers for charge carriers. This composite structure integrates multiple functional properties (photoelectric conversion + charge blocking) into a unified device architecture.
2Measurement precision
If voltage is applied to separate photoconversion and reading timings for global shutter mode, then image quality improves, but energy consumption increases
Solution Approach 1:
The patent implements periodic voltage application to the first electrode to achieve global shutter mode operation. The voltage is applied in periodic cycles: during the photoconversion period, a first voltage is applied to accumulate charges; during the reading period, a second voltage is applied to read the accumulated charges. This periodic voltage switching enables temporal separation of photoconversion and reading operations, improving image quality by preventing charge migration while allowing global shutter functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively reduces parasitic sensitivity by ensuring electrons and holes remain in the photoelectric conversion layer, enhancing the signal-to-noise ratio and enabling global shutter mode operation with reduced distortion.
Implementation Method 1
a photoelectric conversion layer that is located between the first electrode and the second electrode, that contains a donor semiconductor material and an acceptor semiconductor material, and that generates a pair of an electron and a hole
Data Source
AI summary
An imaging device includes pixels. Each of the pixels includes a first electrode, a second electrode, a photoelectric conversion layer that is located between the first electrode and the second electrode, that contains a donor semiconductor material and an acceptor semiconductor material, and that generates a pair of an electron and a hole, a first charge blocking layer located between the first electrode and the photoelectric conversion layer, a second charge blocking layer located between the second electrode and the photoelectric conversion layer, and a charge storage region that is electrically connected to the second electrode and that stores the hole. The difference between the electron affinity of the acceptor semiconductor material and the electron affinity of the first charge blocking layer is larger than the difference between the ionization potential of the donor semiconductor material and the ionization potential of the second charge blocking layer.